Life

Recovery Timing for Perfect Intervals

Everybody loves interval training (right?), but it's not just the work you're doing that counts. The recovery between intervals is important, too. CTS Coach Jim Rutberg explains how it works.

So, you’re all ready to go out for your workout. You have a few gels in your pocket, your bike is gleaming in the warm sun with a bottle of water and bottle of sports drink, your sunglasses are sitting in the helmet draped over your handlebars, and your heart rate monitor/powermeter is quietly waiting to record every last bit of data. Great job, you have all the right gear, but what about your workout timing – specifically the amount of recovery you’re getting between intervals?

Just as intervals of different lengths lead to unique physiological adaptations, manipulating the recovery time you give yourself between intervals can also change the demands – and hence the results – of your workouts. The big question is, how much recovery do you need to get where you want to go?

Intervals that only last 5 to 15 seconds are almost always done at a super-high intensity. We’re talking about your cycling and running or standing starts and accelerations on the bike. To get the most out of each effort, you have to be able to produce maximum power, which means the recovery period between efforts has to allow your muscles to be fully recharged. Such short and intense intervals call upon the ATP-CP system, which is more simply known as the "immediate energy system". To completely oversimplify what’s going on in your muscles, you burn through available ATP in a handful of seconds, and the CP recharges the muscles’ ATP stores to make this important energy source available again. This is why you want to take 5 to 8 minutes of easy recovery walking/jogging/spinning between sprints.

Scenario 2: Short interval – short recovery

These are typically your highest-intensity workouts, like speed work and VO2 intervals. The goal is to make an athlete adapt to repeated maximal efforts, and in order to be effective, it’s imperative that the easy periods between intervals are purposely too short to allow for complete recovery. This means that the easy periods are the same length or shorter than the work period. Fortunately, these intervals don’t need to be very long (30 seconds to 3 minutes); your goal is to add more intervals or an additional set rather than making these efforts 5 minutes long.

Scenario 3: Long interval – 50 to 100% recovery time

Workouts designed to improve your maximum sustainable pace typically feature intervals that are 8 to 20 minutes long, sometimes even longer. The intensity for these intervals is typically at or a little below your lactate threshold, and the idea is to accumulate as much time possible at this workload in order to push your body to adapt. If you’re looking to run a faster marathon or ride a faster century, these are intervals you either are or should be very familiar with. Adequate recovery between efforts – anywhere from 50% of the interval length to the same length of the work period – allows you to maintain the right intensity/pace in your second, third, and maybe even fourth interval. More novice athletes might start with 8 min intervals and 8 min recoveries, but as you get to 12 minutes and beyond you'll be down at the 50% recovery times, or 12 min intervals separated by 6 minutes of recovery. Athletes often make the mistake of shortening their recovery periods during these workouts because they feel rested well before the next interval is supposed to start, and they pay for it when they fade due to fatigue before they should. I don't care if your second interval doesn't feel hard enough; I care that you have the energy to complete your fourth interval at the appropriate pace/power!

Scenario 4: Super-long interval – no recovery

No recovery!? That’s just cruel. In reality, there are times when the work period of an interval is so long that you only need to do one. This is the case with runs or rides at a steady aerobic intensity. The intensity is above your normal cruising pace, but you’re still well within your aerobic system’s capacity to supply the necessary energy. To be effective, these work periods need to be very long and preferably uninterrupted – you want to accumulate as much continuous time as possible at that effort level. These efforts are sometimes split into two or even three intervals for beginners, but more experienced runners, cyclists, and even swimmers benefit more from settling in for the long haul.

Of course, a perfectly structured set of intervals will do you no good if you’re not properly fueled. A pre-workout snack that's high in carbohydrate is a good start. During workouts that are shorter than 60 minutes, focus on fluids and electrolytes during the workout, but not calories. You start with enough calories to get through even the hardest one-hour workout. For your longer workouts you'll want to ingest carbohydrate, fluids, and electrolytes so you have consistent performance right to the last interval. For most athletes during 1 to 4 hour workouts, I recommend an electrolyte drink coupled with calories from GU Gels and Chomps; this allows you match your fluid and electrolyte consumption to your sweat rate while keeping your caloric intake more closely tied to your energy expenditure (20 to 25% of hourly caloric expenditure). And your post-workout nutrition will help you rebuild and be ready for another high-quality session tomorrow.

So get out there, your workouts are waiting for you.

Jim Rutberg is a Pro Coach for Carmichael Training Systems, Inc. and co-author of seven books with Chris Carmichael, including the NYT Bestseller Chris Carmichael’s Food for Fitness and The Time-Crunched Triathlete. CTS is the Official Coaching and Camps Partner of Ironman. To find out about Ironman Coaching and Camp packages, visit www.trainright.com/ironman.